Battle of Issus

The Battle of Issus (5 November 333 BC) was a major battle of Alexander the Great's campaign to conquer the Persian Empire. With an army of 40,850 Macedonian troops, Alexander the Great encamped on the coastal plain of Syria at Issus. The Persian emperor Darius Codomannus and an army of up to 600,000 troops attempted to ambush him, but Alexander was far from dismayed, and he defeated him in a decisive Macedonian victory.

Background
Alexander the Great, leading a large army from Macedon, conquered Asia Minor from the Persian Empire after the Siege of Halicarnassus, which left the Persian-hired Greek mercenary general Memnon of Rhodes dead. The Macedonian army then made camp at Issus on the coastal plain of Syria before they could move farther south into the Levant, with 35,000 Macedonian and Hellenic League troops making their camp on the Pinarus River. Emperor Darius Codomannus of the Persian Empire sent word to all of the corners of his domains, and an army of 110,000 Persian troops gathered behind his banner. He attempted to use his knowledge of the terrain to surprise Alexander's army at Issus, but Alexander was far from dismayed when he found out that Darius had attempted to bring him to battle.

Alexander faced a huge disadvantage because of the vast numerical differences, and the two armies encampedon opposite sides of the Pinarus. The Persian army included Immortals (the elite unit of Persia), Mardian Archers, Greek Mercenaries, and spearmen. The Macedonians had some cavalry in addition to some Cretan Archers and phalangist infantry.

Battle
Alexander ordered a general advance. The tight formation of the Macedonian infantry phalanx lost cohesion moving forward over rough ground and crossing the stream. Darius's infantry were able to penetrate gaps in the bristling barrier of spears and to cut and stab at men in the exposed core of the phalanx. But on the left the Thessalian horsemen performed well against the strongest concentration of Darius's cavalry, while on the right, Alexander led a charge of the companion cavalry that swept all before it. Wheeling in from the flank, Alexander's horsemen bore down upon the rear of the enemy infantry who were driven onto the anvil of the Macedonian phalanx. Darius and his entourage fledthe battlefield to avoid capture. Much of the infantry was trapped and cut down where it stood, while large numbers of fleeing cavalry and skirmishers were pursued and massacred.